In what is the deadliest outbreak of the virus ever, WHO statistics show at least 8,220 people in Guinea, Liberia, and Sierra Leone have died, with another 15 lives claimed in Mali, Nigeria and the United States. Confirmed Ebola cases are now approaching 21,000, and although clinics have been set up in all three countries, the epidemic is far from coming under control.

The report says funerals and burials are still a major source of disease transmission. Despite efforts to educate people about this and to deploy safe burial teams, it’s clear that people are still becoming infected by this route, WHO says.

The new numbers on health care workers show that doctors, nurses and other people working at Ebola treatment centers are among those most vulnerable to the deadly virus. “A total of 838 health-care workers are known to have been infected with Ebola virus disease up to the end of 4 January 2015, 495 of whom have died,” WHO said in a statement.

“The marked increase from the total of 678 health-care worker infections reported last week is due to additional cases reported from Sierra Leone that have occurred since the onset of the epidemic. These are not infections that have occurred between the two most recent reporting periods.”

Because Ebola is transmitted through the bodily fluids of the sick and dead, it is sometimes referred to as the “caretakers’ disease”. Besides healthcare workers, family members of those sickened by Ebola are also at high risk of becoming infected.